Felicia Hardy AKA Black Cat has been both Spidey's lover and enemy, and no matter how tempting it may be, don't ever call her Catwoman.
From the wikipedia:
The Black Cat's father was a world renowned cat burglar. During her freshman year in college, Felicia was date raped by her boyfriend Ryan. Hating the idea of being a victim, she decided that despite the consequences she would murder her rapist. She put aside her studies and began training in various fighting styles and acrobatics. Finally, after months of preparing, she set out for revenge, but before she could find him, Ryan was killed in a drunk driving accident. Furious that she was denied the chance to steal the life of the man who had stolen hers, and feeling reckless, Hardy decided to utilize her new skills to follow in the footsteps of her father.
After amassing a fortune in stolen items, Felicia chose to adopt a costume identity. She first donned the Black Cat costume in order to break her father out of prison. On the same night, she met Spider-Man. Despite her antipathy towards men, Felicia felt a kinship with this lone hero. Spider-Man was the first man she felt she could trust and she grew to love him. Felicia looked for a way to earn his trust and continued with the Black Cat persona as a misguided attempt to attract his affection. Seeing the good in Felicia, Spider-Man made every attempt to have her criminal record expunged.
After a clash with Doc Ock leaving her wounded, Spider-Man barely got her to the hospital in time and as they operated on the dozens of bullet and knife wounds, Peter realized just how much he cared for Felicia. After she recovered they began a relationship and soon Peter revealed his identity to her. But Felicia had great difficulty accepting the fact that Peter was just a man beneath the mask and couldn't understand his need for a civilian life. Peter was hurt, but continued the relationship since it was the first time he didn't need to hide his life as Spider-Man.
At one point, the Kingpin gave her a 'bad luck' power that began to permanently jinx Spider-Man, which was exactly the Kingpin's intent. Feeling a wall of secrets growing between them, Spider-Man broke up with Felicia. He soon realized something was amiss with his own luck and enlisted the aid of Doctor Strange to remove the "hex" on him. But doing so altered the hex's source and changed the Black Cat's powers in the process. She soon found a heightened strength, agility, balance, vision, and retractable claws.
Years later, the Black Cat returned to America to seek out Peter Parker and was devastated when informed by Venom that Peter had married Mary Jane Watson. Angry and jealous, Felicia began harassing the couple, physically threatening Mary Jane and taunting Peter as she dated his friend Flash Thompson. She began to sincerely care for Thompson but he eventually broke up with her when he found out her secret. The Black Cat eventually moved past her feelings of anger and jealousy, and became friends with both Spider-Man and Mary Jane. After Spider-Man used a device to remove his superhuman abilities, the Black Cat aided him in finding the device again in order to restore them. But in the process, the Black Cat's cat-like abilities were completely erased. She subsequently purchased equipment from the Tinkerer to incorporate into her costume in order to compensate for her lost abilities, and occasionally teams up with Spider-Man.